Subject: Aren't mass-energy and potential energy redundant?

Date: Sun May 11 07:48:49 1997
Posted by Patrick Harmon
Grade level: teacher/prof
School: Country Day School
City: San Jose State/Province: No state entered.
Country: Costa Rica
Area of science: Physics
ID: 863354929.PhMessage:

When nuclear rearrangements occur, the rest mass of the nuclei change. The
change in binding energy is then calculated by using the change in rest mass
and Einstein's mass-energy relation (E=mc2). But, it seems that the energy
release during the formation, say, of a helium nucleus can be explained by
the nuclear potential energy released by the protons and neutrons as they are
brought close together. The nuclear force does positive work, making the
change in potential energy negative (meaning the particles are releasing
potential energy) - just as a falling object in a gravitational field turns
gravitational potential energy into kinetic energy. So why is there a change
in rest mass of the nucleons as well? This seems like a redundant reason for
the release of energy in this nuclear process. How does this seemingly double
explanation for the energy release jive with the law of conservation of energy?
Of course, I understand that the same type of mass loss occurs in chemical
reactions, apparently making the concept of chemical potential energy redundant
as well?
Thank you for your consideration of this question!
Patrick Harmon
AP Physics Teacher
Country Day School, Costa Rica